In an IEEE 802.16 (Institute of Electrical and Electronics Engineers 802.16)-based wireless access network, a base station transmits, in every frame, a MAP including information on allocation of resources to users and other information to all mobile stations.
The map includes a downlink (DL) MAP having information on downlink sub-frames and an uplink (UL) MAP having information on uplink sub-frames. Sub-frames having MAP relevance with information included in the DL MAP and the UL MAP are a downlink sub-frame of a corresponding frame and an uplink sub-frame of the corresponding frame designated by an allocation start time field of the UL MAP.
Allocation information is defined in detail by a MAP information element (MAP IE) consisting of the DL MAP and UL MAP.
Transmission/reception such as transmission of acknowledgement (ACK) for DL hybrid ARQ (HARM), channel quality information (CQI) and feedback header transmission, the following DL/UL fixed-allocation, and so on, is performed in a frame scheduled by information acquired from related MAP IE or an uplink channel description (UCD) message, not in a transmission/reception frame designated by MAP relevance.
In an IEEE802.16-based wireless access technique, a method of distinguishing a scheduled frame is not defined, and a mobile station reads a frame number that increases by 1 for every frame and is included in the MAP, thereby distinguishing each frame, and thus determines whether a number of a scheduled frame is the same as a number of a received frame to perceive whether the received frame is the scheduled frame.
However, when the mobile station has failed to demodulate and decode a MAP burst such that it does not acquire MAP information and has a received MAP in a frame after a scheduled frame, since the scheduled frame number is not the same as the number of the received frame, the mobile station continues to wait for the scheduled frame.
Meanwhile, a scheduled frame can be sought by counting the number of frame synchronization signals without using frame numbers. However, when the mobile station loses a frame synchronization signal, it may not exactly perceive the number of frames and thus may transmit or receive data in a frame other than the scheduled frame. If reception is performed in a frame other than the scheduled frame, unnecessary power is consumed. Further, when DL HARQ is performed, a base station requests ineffective retransmission due to cyclic redundancy checking (CRC) error occurrence. If transmission is performed in a frame other than the scheduled frame, the mobile station transmits data through a resource on an uplink sub-frame not having been allocated and thus the base station cannot receive the data, and if the mobile station performs transmission through a resource allocated to anther mobile station, a collision occurs.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.